This invention relates to scintillation cameras used for medical diagnosis and, more particularly, to a gantry for supporting and rotating the detectors of a multi-head scintillation camera around a patient.
In single photon emission computed tomography (SPECT) systems, a camera head rotates around the region (head, heart) to be imaged. Although such an arrangement is operative, it is wasteful, since when the head is in one angular orientation with respect to the patient, radiation at all other angles is not being collected. In addition, it takes a relatively long time to conduct a SPECT study because of the time required to get a complete data set by stepping the head completely around the patient's body.
It has therefore being proposed to rotate simultaneously a plurality of heads around the patient. This results in the collection of more data during a particular interval of time or, alternatively, reduces the time needed to collect a predetermined amount of data, thereby permitting either better images or faster throughput as required by the diagnostician. Furthermore, the newer radioisotopes currently in use have shorter half-lives, so that speed in data collection is essential, since if the data is not collected quickly it disappears.
Three-head camera SPECT units presently available include an annular plate having the three detector heads of the scintillation camera mounted thereon. The plate is attached to a gantry frame and rotates to allow data collection by all the heads at each selected angle around the imaged organ. The detector heads move radially in and out to make either a large or small central opening, depending on the patient's size and the organ being studied. A problem with this type of unit is that the heavy heads and their supports mounted on one side of the annular plate create cantilevered stresses and forces which, because they are not counterbalanced, require massive supporting structures. It is therefore a primary object of this invention to provide a multi-head scintillation camera which is statically balanced in the vertical direction and which therefore does not need a massive gantry.